Many different vehicle systems use hydraulically assisted power steering. For most heavy-duty vehicles, it is the only feasible way to develop the torque needed to turn the vehicle wheels at low speeds. Some lighter-duty vehicles (e.g., small cars) utilize an electrically assisted power steering mechanism that uses only an electric motor directly tied into the steering path. While this is a feasible alternative for smaller vehicles, electrically assisted power steering mechanisms generate insufficient force to assist steering a heavy-duty vehicle chassis due to the significantly increased torques needed to steer the wheels.
Some hybrid vehicles utilize an electrically powered hydraulic steering system. In such electrically powered hydraulic steering systems, the electric motor can be controlled on fixed speed basis. That is, the steering assist electric motor continuously runs at the same speed while the vehicle is running, which is highly inefficient and increases wear on all components.
In some cases, difficulties also may arise when trying to add sensors to a steering system to measure driver torque applied to the steering wheel. Using steering sensors alone, for example, as in some electrically-driven power steering systems, can lead to overly complex control methods and poor driver steering feel.
The present disclosure addresses some of these aspects of the prior art and/or other aspects of the prior art.